This invention relates to heat sinks and, more particularly, to heat sinks including fans and heat pipes.
Semiconductors, including microprocessors and other integrated circuits (ICs), generate heat during use. Current microprocessors, for example, can emit 50 watts of power or more. The temperature of the microprocessor or IC has a direct impact upon its performance. Empirical studies have shown that the failure rate doubles for every 10xc2x0 C. increase in the junction temperature (i.e., the temperature of a transistor within the IC).
Unless microprocessors and other ICs are thermally managed during use, they will not operate reliably. Failures include phenomena such as junction fatigue, electromigration diffusion, thermal runway, and electrical parameter shifts. For most uses of a semiconductor device, a proper mechanism for heat dissipation is needed.
Heat may be transferred from the device by convection, radiation, or conduction. Convection is the transfer of heat by moving air. Radiation is the transfer of heat from one surface to another via electromagnetic waves. Conduction is the transfer of heat between two solids, from a higher temperature object to a lower temperature one. Each of these principles may have a part in the operation of heat sinks.
Heat sinks are devices that attach directly to a semiconductor or other hot surface to enhance heat dissipation from the surface. Heat flows from the surface to cooler air through the heat sink. A heat sink is generally designed with a first surface, for engaging with the semiconductor, and a second surface, for contact with the cooler air. The second surface, often formed of a plurality of projections or fins, is designed for maximum surface area, and thus maximum contact with the air, to allow heat to dissipate more quickly.
To further facilitate air flow from the hot surface, many heat sinks include small fans mounted thereon. Heat pipes may also form part of the heat sink, allowing heat transfer to the liquid or gas within the pipes. The heat sink may be painted or anodized to enhance the effect of radiation heat transfer.
Another consideration when designing a heat sink is weight. Although copper-based heat sinks may be preferred over aluminum due to better heat transfer results, copper is a heavier material. A typical copper-based heat sink with a fan, for example, is over 500 grams in weight. A 450-gram heat sink has been shown to deflect a printed circuit board (PCB). The deflection of the PCB can cause component damage as well as damage to the PCB traces and solder pads.
Thus, there is a continuing need to support a heat-producing integrated circuit with a lightweight heat dissipating heat sink.